/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.oxm.support;

import java.io.IOException;
import javax.xml.transform.Source;
import javax.xml.transform.sax.SAXResult;
import javax.xml.transform.sax.SAXSource;

import org.xml.sax.ContentHandler;
import org.xml.sax.DTDHandler;
import org.xml.sax.EntityResolver;
import org.xml.sax.ErrorHandler;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.SAXNotRecognizedException;
import org.xml.sax.SAXParseException;
import org.xml.sax.XMLReader;
import org.xml.sax.ext.LexicalHandler;

import org.springframework.lang.Nullable;
import org.springframework.oxm.Marshaller;
import org.springframework.util.Assert;

/**
 * {@link Source} implementation that uses a {@link Marshaller}.Can be constructed with a
 * {@code Marshaller} and an object to be marshalled.
 *
 * <p>Even though {@code MarshallingSource} extends from {@code SAXSource}, calling the methods of
 * {@code SAXSource} is <strong>not supported</strong>. In general, the only supported operation on this class is
 * to use the {@code XMLReader} obtained via {@link #getXMLReader()} to parse the input source obtained via {@link
 * #getInputSource()}. Calling {@link #setXMLReader(XMLReader)} or {@link #setInputSource(InputSource)} will result in
 * {@code UnsupportedOperationException}s.
 *
 * @author Arjen Poutsma
 * @see javax.xml.transform.Transformer
 * @since 3.0
 */
public class MarshallingSource extends SAXSource {

    private final Marshaller marshaller;

    private final Object content;


    /**
     * Create a new {@code MarshallingSource} with the given marshaller and content.
     *
     * @param marshaller the marshaller to use
     * @param content    the object to be marshalled
     */
    public MarshallingSource(Marshaller marshaller, Object content) {
        super(new MarshallingXMLReader(marshaller, content), new InputSource());
        Assert.notNull(marshaller, "'marshaller' must not be null");
        Assert.notNull(content, "'content' must not be null");
        this.marshaller = marshaller;
        this.content = content;
    }


    /**
     * Return the {@code Marshaller} used by this {@code MarshallingSource}.
     */
    public Marshaller getMarshaller() {
        return this.marshaller;
    }

    /**
     * Return the object to be marshalled.
     */
    public Object getContent() {
        return this.content;
    }

    /**
     * Throws a {@code UnsupportedOperationException}.
     */
    @Override
    public void setInputSource(InputSource inputSource) {
        throw new UnsupportedOperationException("setInputSource is not supported");
    }

    /**
     * Throws a {@code UnsupportedOperationException}.
     */
    @Override
    public void setXMLReader(XMLReader reader) {
        throw new UnsupportedOperationException("setXMLReader is not supported");
    }


    private static class MarshallingXMLReader implements XMLReader {

        private final Marshaller marshaller;

        private final Object content;

        @Nullable
        private DTDHandler dtdHandler;

        @Nullable
        private ContentHandler contentHandler;

        @Nullable
        private EntityResolver entityResolver;

        @Nullable
        private ErrorHandler errorHandler;

        @Nullable
        private LexicalHandler lexicalHandler;

        private MarshallingXMLReader(Marshaller marshaller, Object content) {
            Assert.notNull(marshaller, "'marshaller' must not be null");
            Assert.notNull(content, "'content' must not be null");
            this.marshaller = marshaller;
            this.content = content;
        }

        @Override
        public void setContentHandler(@Nullable ContentHandler contentHandler) {
            this.contentHandler = contentHandler;
        }

        @Override
        @Nullable
        public ContentHandler getContentHandler() {
            return this.contentHandler;
        }

        @Override
        public void setDTDHandler(@Nullable DTDHandler dtdHandler) {
            this.dtdHandler = dtdHandler;
        }

        @Override
        @Nullable
        public DTDHandler getDTDHandler() {
            return this.dtdHandler;
        }

        @Override
        public void setEntityResolver(@Nullable EntityResolver entityResolver) {
            this.entityResolver = entityResolver;
        }

        @Override
        @Nullable
        public EntityResolver getEntityResolver() {
            return this.entityResolver;
        }

        @Override
        public void setErrorHandler(@Nullable ErrorHandler errorHandler) {
            this.errorHandler = errorHandler;
        }

        @Override
        @Nullable
        public ErrorHandler getErrorHandler() {
            return this.errorHandler;
        }

        @Nullable
        protected LexicalHandler getLexicalHandler() {
            return this.lexicalHandler;
        }

        @Override
        public boolean getFeature(String name) throws SAXNotRecognizedException {
            throw new SAXNotRecognizedException(name);
        }

        @Override
        public void setFeature(String name, boolean value) throws SAXNotRecognizedException {
            throw new SAXNotRecognizedException(name);
        }

        @Override
        @Nullable
        public Object getProperty(String name) throws SAXNotRecognizedException {
            if ("http://xml.org/sax/properties/lexical-handler".equals(name)) {
                return lexicalHandler;
            } else {
                throw new SAXNotRecognizedException(name);
            }
        }

        @Override
        public void setProperty(String name, Object value) throws SAXNotRecognizedException {
            if ("http://xml.org/sax/properties/lexical-handler".equals(name)) {
                this.lexicalHandler = (LexicalHandler) value;
            } else {
                throw new SAXNotRecognizedException(name);
            }
        }

        @Override
        public void parse(InputSource input) throws SAXException {
            parse();
        }

        @Override
        public void parse(String systemId) throws SAXException {
            parse();
        }

        private void parse() throws SAXException {
            SAXResult result = new SAXResult(getContentHandler());
            result.setLexicalHandler(getLexicalHandler());
            try {
                this.marshaller.marshal(this.content, result);
            } catch (IOException ex) {
                SAXParseException saxException = new SAXParseException(ex.getMessage(), null, null, -1, -1, ex);
                ErrorHandler errorHandler = getErrorHandler();
                if (errorHandler != null) {
                    errorHandler.fatalError(saxException);
                } else {
                    throw saxException;
                }
            }
        }
    }

}
